Amphisbaena, Rochester Bestiary, c.1230

The amphisbaena is a fascinating snake with two heads—one at its tail and one at its normal head. This unique feature allows it to move in both directions, earning its name which means "running from both ends." Unlike other snakes, the amphisbaena boldly exposes itself to the cold and sheds its skin during winter. Lucan captures its eerie presence, describing it as "grievous, turning toward its two heads," with eyes that shine like lamps.

Legend has it that this snake was born from the blood dripping from Medusa’s head, when Perseus killed it. According to Pliny and folk medicine, when women wore the snake around their necks, they could expect to have a safe pregnancy but if they wanted to cure arthritis or the cold, they just needed to wear its skin only.

Est serpens duo habens capita. unum in cau-
da. et alterum in loco suo. et ex utroque ca-
pite currit. Unde dicitur amphivena. quasi ex am-
babus partibus currens. Hec sola serpentium frigori se com-
mittit. it ut hieme eximiam deponat. Unde lu-
canus. Est gravis ingeminum vergens capud am-
phivena. Cuius oculi lucent velut lucerne.

There is a snake with two heads, one at its tail and the other in its proper place and it moves from both heads. Hence, it is called amphĭsbaena , meaning running from both ends. Only this snake among all the others exposes itself to the cold and sheds in winter. Thus, Lucan says thereof: "Grievous is the amphisbaena, turning toward its two heads. Its eyes shine like lamps."

Footnotes

[1] This snake is a mythological creature that eats ants with a head at each end. https://en.wikipedia.org/wiki/Amphisbaena

[2] Lucan, Civil War 9.717: "Grievous is the amphisbaena, turning toward its two heads. Its eyes shine like lamps."